Drosera prostrata — Vorstman's Guide to the Carnivorous Plants

Identification

A perennial tuberous plant that spreads four to five prostrate lateral stems 3.5 to 15 cm long over the sand. Along them stand the fan-shaped trapping leaves typical of the section. This prostrate habit is the character that separates it from its relatives within section Stolonifera. Flowering in May and June; FloraBase records yellow flowers. Exact leaf and flower measurements are not published in the sources consulted.

Similar species

Its closest relative is Drosera stolonifera, under which it was originally placed as a subspecies; that has two or three obliquely ascending lateral stems and grows much further south, in wet heath around Perth. Drosera rupicola has semi-erect lateral stems and grows by granite outcrops inland; D. ramellosa and D. platypoda have erect stems. Within the northern range of D. prostrata, the prostrate habit is practically decisive.

The trap and how it works

An active flypaper trap with a leaf shape of its own. The leaves are fan-shaped: a narrow base widening into a blade whose upper edge is set with long tentacles, sometimes in whorls of three or more along the stem. Small insects that walk into that edge or land on it stick to the droplets, after which the tentacles bend over the prey and the glands secrete enzymes. As in all tuberous sundews, much of the nitrogen and phosphorus absorbed goes into the tuber that has to carry the plant through summer. Because the stems lie flat, the trapping leaves sit just above the sand and catch mostly crawling and low-flying insects.

Habitat and ecology

Well-drained sandy soils on sandplains: yellow sand, sometimes mixed with white or red sand (D1), with open, low heath and scrub (B5). This is a drier setting than that of most relatives, which grow in winter-wet hollows.

Distribution and elevation

Endemic to Western Australia: from the Tamala area near Shark Bay south to Binnu. FloraBase lists the Geraldton Sandplains and Yalgoo bioregions. Altitudinal limits are not published.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 3 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

N.G. Marchant and Allen Lowrie described the plant in 1992 as Drosera stolonifera subsp. prostrata; Lowrie raised it to species rank in 2005 in the journal Nuytsia. That fits a wider pattern: between 1982 and 2011 nearly all the former subspecies of D. stolonifera were raised to species. No further forms are recognised within D. prostrata.

Where and when to see it

May and June are the months: early in the wet season, when the prostrate stems have grown out and the plant is in flower. Search open patches in the heath of the northern sandplains and look low over the sand. In summer there is nothing to see above ground.

Conservation status

Assessed as Least Concern (LC) on the IUCN Red List; not listed in CITES, and rated not threatened in FloraBase. Part of the range lies in little-cleared country. The sources consulted name no specific threats.

Scientific name

Drosera prostrata | (Marchant & Lowrie) Lowrie, 1992

Drosera prostrata was first described in 1992 by Neville Gordon Marchant and Allen Lowrie as a subspecies, Drosera stolonifera subsp. prostrata, in Kew Bulletin, volume 47, page 320. In 2005 Lowrie raised the taxon to full species rank, in Nuytsia, volume 15(3), page 374. The type specimen was collected by Allen Lowrie on 14 June 1984, along the road to "The Loop" near Kalbarri, in south-western Western Australia. The specimen is held in the PERTH herbarium (number PERTH 4179005). The epithet prostrata is Latin for "prostrate" or "lying flat" (from prosternere, "to throw down"). It refers to the characteristic prostrate growth habit of the lateral stems, which sets this species apart from all other members of section Stolonifera. It is a descriptive name.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.